Diversity reception radio receivers are well known in the art. Such receivers have been used to substantially improve radio reception in a changing multipath environment. Diversity receivers are particularly desirable in mobile and portable applications, in which a receiver may be moved into an isolated weak signal area caused by self-cancellation of multipath signals.
One conventional approach to a diversity receiver has comprised a dual antenna space-diversity system, the dual antennas coupled to a switch for selectively coupling one of the dual antennas to a single receiver. During operation the receiver is switched to an alternate antenna in response to a signal received from a currently selected antenna deteriorating below a predetermined switching threshold. This approach has a drawback in that the approach does not always select the antenna having the stronger signal. For example, a currently selected antenna having a signal marginally above the predetermined switching threshold would remain selected, even though a signal from a non-selected antenna is much stronger.
Another conventional approach to the diversity receiver has comprised a dual space-diversity antenna system separately coupled to dual receiver elements for amplifying and demodulating a radio signal received by the dual antennas. Such receivers have typically utilized an electronic switch to select the "best" output signal from one of the dual receiver elements based upon a measurable selection criterion, such as signal-to-noise ratio. Unfortunately, while the dual receiver approach to diversity reception has provided performance superior to the single receiver approach, it has typically been an expensive and power-hungry approach. This is because the dual receiver approach has required significantly more receiver circuitry than the single receiver approach.
Thus, what is needed is a way of building a diversity receiver that provides the cost and power advantages of a single receiver, switched antenna approach, but that can continuously select the antenna feed having the stronger signal.